Electrosensitive printing apparatus with print head continuously moved across paper



Jan. 24, 1967 2. YAZEJIAN ETAL 3,300,017

. ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER 11 Sheets-Sheet 1 Filed April 30, 1965 Jan. 24, 1967 2.YAZEJIAN ETAL 11 Sheets-Sheet 2 Filed April 50, 1965 mommmuomm 29mm NW5.MES llllllllll 55% 625080 028mm 18 56 mwm 526% m m bzwsm o2 ..A; m mmnzmnu nu Rm wk Em fin Rm wk Rm Em w #273182 {ill} QZOmPQMJM Jan. 24, 19672. YAZEJIAN ETAL 3,300,017

ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER 11 Sheets-Sheet 15 Filed April 30, 1965 I IIIJIIIIIIIIIIIIIIIIIIII 1967 2. YAZEJIAN ETAL 3,369,017

ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER Filed April 30, 1965 ll Sheets-Sheet 5 Jan. 24, 1967 2.YAZEJIAN ETAL 3,3 W

' ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER 7 1'1 Sheets-Sheet 6 Filed April 30, 1965 FIG. 9.

F 16. ll.

1967 z. YAZEJIAN ETAL 3,300,017

ELECTROSENSITLVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER Filed April 50, 1965 ll Sheets-Sheet 7 Jan. 24, 1967 z.YAZEJIAN ETAL 3,300,017

ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT Filed April 30, 1965 HEADCONTINUOUSLY MOVED ACROSS PAPER 11 Sheets-Sheet 8 24, 1967 z. YAZEJIANETAL 3,300,017

ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER Filed April 30, 1965 ll SheetsSheet 9 Jan. 24, 1967 z.YAZEJIAN ETAL 3,300,017

ELECTROSENSITIVE PRINTING APPARATUS WITH PRINT HEAD CONTINUOUSLY MOVEDACROSS PAPER Filed April 30, 1965 ll Sheets-Sheet 1O Jan. 24, 1967 2.YAZEJIAN ETAL ELECTROSENSITIVE PRINTING APPARATUS WITH PR1 HEADCONTINUOUSLY MOVED ACROSS PAPER 11 Sheets-Sheet 1 1 Filed April 30, 1965FIG. /6.

United States Patent 3,300,017 ELECTROSENSITIVE PRINTING APPARATUS WITHPRINT HEAD CONTINUOUSLY MOVED ACROSS PAPER Zaven Yazejian, Mahopac,N.Y., and Jerome R. Fuld, Trumbull, and Walter V. Benkler, East Norwalk,Conn., assignors to Sperry Rand Corporation, New York, N.Y., acorporation of Delaware Filed Apr. 30, 1965, Ser. No. 452,273 16 Claims.(Cl. 1971) The invention relates in general to printing apparatus andmore particularly to an apparatus for printing data electrically orelectrosenitive record material.

Certain known printing arrangements provide a plurality of styli in apatterned arrangement capable of producing characters through selectivetime energization of the styli as the printer is swept across the faceof the record material. The styli are physicalyl separated andelectrically isolated from each other in a pattern most conducive to thegeneration of the desired characters.

In such systems the styli rest directly upon the record material andcurrent is caused to pass from the selected styli through the recordmaterial to a ground plate located at the opposite side of the recordmaterial, or from one styli through the paper to another styli. Thecurrent in passing through the record material causes distinct marks ordots which can be combined through proper timed energization of thestyli to form the data to be printed.

The present invention provides a print head drive mechanism for use withsuch a styli printing arrangement and serves to drive the print headacross the record paper in a carefully timed and synchronized manner soas to insure proper printing of output data and to effect control in acompletely automatic manner of the print operation.

It is therefore an object of the instant invention to provide a printhead drive mechanism for use with a printing arrangement of the typedescribed capable of effecting accurately timed reciprocation of anelectronic print head across the surface of a record paper.

It is a further object of the instant invention to pro vide a print headdrive mechanism for use in a printer of the type described capable ofproviding automatic control of the printing operation includingcarefully timed reciprocation and return of the print head and automaticretraction thereof during the return excursion.

It is still a further object of the instant invention to provide a printhead drive mechanism capable of driving the print head across the recordpaper and efiecting return thereof to the start position automaticallyin response to print head position.

It is still another object of the instant invention to provide a printhead drive mechanism for use with a printer of the type describedwherein both automatic and manual control for positioning of the printhead and other elements of the printer mechanism are provided.

The many objects and advantages of the instant invention can be seenfrom the above discussion, and will be further clarified by thefollowing description when taken in conjunction with the accompanyingdrawings wherein:

FIGURE 1 is a simplified schematic view in perspective of portions of aprinter in accordance with the invention;

FIGURE 2 is a simplified schematic view greatly enlarged of the printinghead of FIGURE 1, showing the configuration of the styli matrix;

FIGURE 3 is a schematic, cross-sectional view in side elevation andgreatly enlarged of a pair of pin styli taken through the printing headof FIGURE 1;

FIGURE 4 is a side view of the print head partially in section;

FIGURE 5 is a simplified schematic block diagram of the energizingcircuits for the printing head;

FIGURE 6 is a front view of the print head drive mechanism in accordancewith the instant invention;

FIGURE 7 is a top view of the print head drive mechanism illustrated inFIG. 6;

FIGURE 8 is a detail front view of the print head drive mechanism inaccordance with the invention illustrated in FIG. 6 with portionsthereof cut away to illustrate the detail thereof;

FIGURE 9 is a side section view through the print head drive mechanismof FIG. 6;

FIGURE 10 is a side view of the print head drive mechanism of theinvention;

FIGURE 11 is a detail view of the cam arrangement for retracting thepressure rollers associated with the platen of the printer;

FIGURE 12 is a left side view of the printer arrangement of the instantinvention;

FIGURE 13 is a simplified detail view illustrating the print headretracting mechanism in accordance with the instant invention;

FIGURE 14 is a side section view of the printer mechanism illustratingthe print head drive controls in accordance with the instant invention;

FIGURE 15 is a top section detail view of the print head drive controlsillustrated in FIG. 14; and

FIGURE 16 is a detail front view of the print head drive controlillustrated in FIG. 14.

Referring now to the drawings for a detailed description of the presentinvention, and more specifically to FIG. 1, a stylus or printing head,generally designated by reference numeral 334 is slidably mounted on aguide rod 336 for movement transversely of record paper 330, or the likeat the printing position. Printing head 334 may be driven by anysuitable means from a starting point at the left edge of record paper330, the initial printing position, to the right edge of the paperduring the printing cycle, and then back to the left edge, inpreparation for printing the next line. Such driven movement is effectedat a substantially constant speed by the printing head conveyingmechanism of the invention to be described in detail hereinafter, whichtransmits driven motion to printing head 334 by means of a timing belt338 attached by fasteners 340 to printing head 334. It is to beunderstood that incident to printing head 334 being returned to itsinitial printing position at the end of a printing cycle, roller 332 ofthe record paper conveyor moves tape 330 in the direction of thedirectional arrow a to place the next printing line of paper 330 intoprinting position.

Printing head 334 is formed of an electrically nonconductive materialand is provided in the illustrated embodiment with sixteen individualstyli assemblies 342 (FIGURE 3), each having a stylus or electrode inthe form of a rod-like pin 344. The pins are designated P1 through P16(FIGURE 2) to differentiate the pins from one another. Styli pins 344(FIGURE 3) protrude from the bottom of printing head 334, fourteen ofwhich pins (P1P14) are arranged into a matrix having the configurationof a digit 8 slightly slanted to the left, as seen in the bottom view ofthe printing head 334, shown at FIGURE 2. In addition a pair of pins, Pand P16, are provided for inserting the decimal point designation in theproper position between numerals along the line of print.

The pin 344 of each styli assembly 342 is formed of conductive material,preferably of tungsten and is slidably disposed in an associated pinhole or channel 348 defined in a bottom portion 352 of printing head334. Each pin 344 is provided with a sleeve 354 of conductive material,such as stainless steel, which sleeve is press fit onto the upper end ofthe pin. Sleeve 354 is slidably confined in a channel 356 aligned withchannel 348 and defined in an intermediate portion 358 of printing head334 to permit up and down movement of pin 334 and sleeve 354 in channel356. A biasing spring 362 of the coil type and of conductive material isprovided for each pin 344 and is loosely disposed under compression inthe channel 356 provided for its associated pin. Spring 362 pressesagainst sleeve 354 of its associated pin 344, biasing the pin downwardto maintain the free or lower end of the pin in constant contact withthe upper surface of record paper 330. Downward movement of pin 344 islimited by its sleeve 354 abutting a shoulder 364 formed by printinghead portion 352 where channel 348 joins channel 356.

An electrical connecting lead 366 is provided for each pin 344 andextends through a hole 368 defined in a portion 370 of printing head334. Each lead 366 enters the channel 356 of its respective pin 344 andis connected electrically to the uppermost portion of the spring 362 insuch channel. The leads 366 serve to connect their respective pins 344(P1P16) to the pin energizing circuits.

It may be noted that with the described mounting arrangement of eachstyli assembly 342, each styli pin 344 is individually spring biased tocontinually bear upon and frictionally engage the top surface of recordpaper 330, as printing head 334 is driven transversely of the tape. Suchindividual spring biasing automatically compensates for unevenness ofthe tape surface and for variation in the wear rates of the individualstyli pins 344. However, this direct contact of the styli pins with thepaper surface has a tendency, should the styli pins be exposed from theprint head, to pick up fibers from the paper, dust particles and otherforeign matter which shortly will cause a fouling of the print headconsiderably reducing, if not altogether disrupting, the printcapability of the arrangement.

As a result of the difliculties with fouling of the print head, a boot350 is positioned over the print head as seen in FIG. 4, which bootconsists of a cap 351 made from phenolic or similar material and agasket 353, made from a thermoplastic resin such as that which iscommonly known and sold under the trademark Teflon. The boot 350 isprovided with a plurality of holes, each in substantialy alignment withone of the styli pins of the printing head so that the individuallyspring biased styli pins may protrude through the boot and contact therecording surface of paper 330.

The boot 350 is spring loaded with respect to the print head by springs380 (one shown) recessed in channels or grooves 381 in the cap 351. Thesprings 380 act upon pins 382 in contact with the collar 384 surroundingthe print head. The bias provided by springs 380 forces the Teflongasket 353 against the surface of record paper 330 so that the stylipins 344 are completely isolated except for the cross-sectional endswhich contact the surface of the tape.

Since the Teflon gasket is in pressure contact with record paper 330when the print head assembly is in the print position, the end of thecap and Teflon gasket have a radius comparable to that of the roller 332so as to insure good contact between the gasket and the paper over thefull gasket area. The holes in the cap 350 through which the print pinspass have a dimension only slightly larger than the pins themselves;however, due to the natural lubrication provided by the Teflon material,the pins may very easily slide in and out of the print head in responseto pressure by the springs 362 insuring good contact between the pins344 and the surface of record paper 330.

While the boot 350 is shown as being formed of two separate elements 351and 353, it is within the purview of the invention to provide the entireboot of a single material such as fluorocarbon resin with a filler so asto combine the low friction and high dielectric properties of Teflonwith low wear and rigidity. In addition, gasket 353 may be made fromother materials having properties similar to Teflon.

When the print head is released to the print position, the outer surface355 of bottom portion 352 (FIGURE 3) is stopped before engaging insidesurface 356 of the cap 351 by a stop 385 (FIGURE 4) on the capcooperating with suitable means (not shown) so that a gap 357 isprovided therebetween. The individually biased styli pins 344 protrudeslidably through the boot 350 to engage the record surface 330. Thespring bias on the boot relative to the print head places the frontsurface of the Teflon gasket 353 firmly but resiliently against therecord surface to be printed upon. Thus, the styli pins 344 arecompletely surrounded by the boot 350 so that only the cross-sectionalend surfaces of the pins are exposed and these firmly contact thesurface of paper 330. In this position, the record sheet engaging endsof the pins are substantially in the same plane as the outer surface ofthe Teflon gasket 353.

Wtih such an arrangement, the gasket 353 which follows the record sheetcurvature is maintained firmly against the record surface as it and theprint head are driven transversely of the record sheet. The Teflon sheetbiased against the record surface eliminates the gap which washeretofore present between the print head and the record sheet and inwhich dust particles accumulated, fouling the pins.

In addition to the elimination of such gap, and the relatively tight fitof the pins as they pass through the Teflon gasket, the gasketeffectively mashes the exploded dust particles of the record sheetsurface back into the sheet surface such that no noticeable loose dustparticles are formed to foul the pins. This wiping action of the Teflongasket as it moves across the record surface under pressure forcing thedust particles back into the surface impregnates the surface with allloose particles preventing these particles from entering the pinchannels in the print head and from generally fouling the styli or otherportions of the printing arrangement.

In addition to solving the fouling problem, as indicated above, theprovision of the boot 350 over the print head provides an added supportfor the styli pins over substantially their entire length to the veryends which contact the record surface of paper 330 resulting in anincreased stability and more accurate registration of the pins so thatgreater clarity in printing is achieved and scratching of the surfacedue to vibrations in the pin is completely eliminated.

By selectively electrically pulsing certain combinations of pins 344 ofthe styli matrix of FIG. 2, the configurations of numerals 0 through 9and some special symbols may be printed upon record paper 330 (FIG. 1),as print ing head 334 is moved transversely thereto. Such marking iseffected in the preferred embodiment by causing a succession of currentpulses to flow from one pin 344 (FIG. 3) along the chemically coatedsurface of conductive record paper 330 to a second pin 344 which isassociated with and spaced from the first pin. For example, with thepair of pins P1, P2 shown in FIG. 3, a pulse of current may be caused toflow successively from P1 along record paper 330 to pin P2. Such currentflow causes chemically treated tape 330 to darken or change color at thetwo points where pins P1 and P2 engage the tape surface to providelegible distinct marks thereat, which due to successive pulsationsthereof may take the form of elongated dots or lines.

The electrical pulsing of the pins is substantially instantaneo us, suchthat movement of printing head 334 relative to record paper 330 iseffectively stopped during relative motion between pin 344 and recordpaper 330 during the printing.

The sixteen styli pins 334 (Pl-P14, FIG. 2) comprising the digit 8 stylimatrix and a decimal point designation as mentioned above, areelectrically connected to the pin energizing circuits in pairs.

The pin styli 344 are therefore divided into pin pairs and an electricalstyli energizing circuit (FIGURE 5) is provided for each pair of pins.Thus, eight pin energizing circuits, or driving circuits 371378 areutilized for energizing the sixteen pins. The digits 0 and 1 through 9,plus certain symbols, such as the letter C and the decimal point may beprinted by causing the driving circuits to successively energizeselective pin pair combinations in accordance with a particular timesequence.

The driving circuits utilize means in the form of a decoding matrix 383for detecting the input of certain pin selection signals derived from aninput processor. The decoding matrix translates the selection signalsand conditions the driving circuits to eifect subsequent energization ofassociated pin pairs, or to prevent such energization, as to the signalsdictate. The detecting means also automatically and continually respondsto changes in pin selection as denoted by the selection signals.

A print signal causes energization of print initiating means (not shown)which generate initiating or gating signals which are appliedsimultaneously to all driving circuits via the decoding matrix 383. Thiscauses the driving circuits of the selected pin pair combination to besimultaneously energized to form the desired character on the recordmedium, while those of the unselected pin pairs are maintainedunenergized in accordance with the preconditioned state of the drivingcircuits. The print initiating signals are in the form of electricalpulses.

During printing, the printing head 334 is moved at a substantiallyconstant speed transversely of the record paper 330. Selection of thepin pairs to be energized and pulsing of their respective drivingcircuits are synchronized with transverse movement of the print headsuch that desired characters are printed sequentially on a print line.In this way, energization of selected pin pairs in response to thecommon print initiating pulses will be sufficiently instantaneous so asto appear to stop relative motion between the print head and recordmaterial, producing distinct printed characters on the record material,notwithstanding such relative motion.

Such an arrangement obviates the need to use a ground plate required insome systems, and minimizes the amount of equipment required for properoperation. The simultaneous energization of selected pin pairs by thecommon print initiating signals to print a character on :the recordmedium also provides a highly reliable printing arrangement at minimalcost.

The print head drive mechanism of the instant invention as seen in FIGS.6 and 7, includes the print head 334 .mounted on guide shaft 336 forsliding movement along the shaft length from the extreme left handmargin to the extreme right hand margin of the record paper 330. Theguide shaft 336 for the print head is secured eccentrically of a pair ofrotatable discs 501 and 502, seen most shows in detail disc 501 inregistration with the aperture in bracket 510.

A platen or paper roller 332 is secured to shaft 506 (FIG. 8) bysuitable means, such as set screws 508, which shaft 506 is notatablysupported in the side support plates 514 and 516. The paper 330 is heldagainst the platen 332 by three sets of pressure rollers 518, 520 and522, all of which are shown in the FIG. 7 top view. The two sets ofrollers 518 and 520 each consist of pairs of individual rollers mountedon respective stud shafts 519 and 521, guided in slots 517 and 523(FIGS. 9 and 10) in the side support plates 514 and 516. The rollers 518and 520 are spring biased into pressure contact with the platen 332 bysprings 523 and 525 (FIG. 7) secured to a common pin 515 one each ofwhich is fastened to the side support plates 514- and 516. The rollers522 are mounted on a spring loaded shaft 526 guided in slots 527 in theside support plates 514 and 516. The shaft 526 is spring loaded to pins(not shown) secured to the side support plates 514 and 516 by means ofsprings 528 (FIG. 10).

The pressure rollers 518 also support a transparent tear bar assemblyconsisting of a tear bar 531 (shown in FIGS. 6 and 9 only for purposesof clarity) supported by suitable bracket 532 on the stub shafts 519 ofthe pressure rollers.

In order to retract the pressure roller sets 518, 520 and 522 from thesurface of the platen 332, for example during paper insertion, a lever530 and actuating bar 537 are pnovided inter-connecting a pair of cams535 (FIG. 11) and 536 (FIG. 9) mounted on the platen support shaft 506on either side of the platen 332, such that cam surfaces on the cams 535and 536 contact the shafts 519, 521 and 526 of the three pressure rollersets and force the rollers outwardly from the platen 332 in response toclockwise rotation (direction arnow b) of the cams by the lever 530, asseen in phantom line in FIG. 11..

The paper support bar 529 which extends between the side support plates514 and 516 also serves as an abutment for the lever 530 determining thestarting position thereof. The springs biasing the various barsassociated with each of the sets of pressure rollers serve to naturallyforce the lever 530 against the paper support bar 529 unless pressure isapplied thereto, to oppose the natural bias of these springs.

A paper feed guide 539, seen most clearly in FIG. 9, is positionedbeneath the platen 332 and supported by the side support plates 514 and516. The guide 539 serves the well known purpose of maintaining thepaper against the bottom side of the platen 332 and guides the paperupwardly between the print head 334 and the platen. In order toaccommodate the pressure rollers 520 and 522 the guide 539 is providedwith suitable apertures through which the rollers may extend to pressthe paper against the platen.

The above-described combination including the platen, sets of pressurerollers, paper tear and support bars and the paper guide, are commonprinter and typewriter elements which may obviously be provided in aform different from that described and illustrated herein. In addition,other means for supporting these members with relation to one anothermay be provided in accordance with well-known conventional techniqueswithout departing from the spirit and scope of the instant inventionwhich relates more specifically to the means described hereinafter foreffecting drive of the print head across the record paper and controlthereof in accordance with requirements for effecting proper printing. Ameans for retracting the pressure rollers other than the specific carns'535 and 536 may also be provided; however, as will be seen hereinafter,these cams in combination with other control elements of the system makepossible a simplified control of the print head and pressure roller setsduring operation of the printing mechanism.

Looking more closely to the construction of the print head 334, as seenin FIGS. 6, 8 and 9, the pin carrying portion 540 of the print headforms an integral print head construction with the cylindrical bodymember 541. The print head 334 is mounted to the guide bushing assembly545 by flanges 542 on the print head secured to an upright flange 543forming part of the bushing assembly.

The bushing assembly is formed primarly of hollow housing member 546(FIG. 8) which surrounds the guide shaft 336 and is spaced therefrom bya pair of tubular bushings 547 made preferably of a synthetic materialsuch as Teflon or any other known self-lubricating material suitable forserving as a bearing means between the housing member 546 and the guideshaft 336. A thin jacket or casing 548 almost completely surrounds the,assembly 545 providing the flange 543 and insuring that the elements ofthe assembly are maintained in proper position.

The print head 334 and guide bushing assembly 545 are freely rotatablymounted on the guide shaft 336 and are maintained in proper uprightposition with respect to the platen 332 by a slide bar 550 riding in aslot 551 provided in a longitudinally extending guide member 552positioned beneath the platen 332, as illustrated in FIG. 9. The guidebar 552 extends at least between the limits of print head scan andserves to maintain the print head 334 in a proper upright position atall times. The slide bar 550 is provided at its extreme end with abushing member 553 which rides on the inner surface of the channel 551maintaining the end of the slide bar 550 at a proper distance from thechannel and facilitating the sliding movement thereof.

The slide bar 550 is secured to the bottom of the guide bushing assembly545 by means of screws or other suitable fastening means secured throughthe slide bar 550 and into the housing member 546 and the tubular guidebearings 547, thereby not only fastening the slide bar to the bushingassembly 545 but also serving as a key preventing relative rotationbetween the guide bushings 547 and the housing member 546.

The guide bushing assembly 545 is clamped to the timing belt 338 bymeans of a clamp formed by opposed clamping jaws 555 and 556 clamped tothe belt by means of screws 340. The clamp is secured to the guidebearing assembly 545 by means of opposed projections 557 formed on theclamping jaw 555 and interlocking with corresponding projections 558 onthe housing member 546 thereby locking the clamp to the bushingassembly. In order to prevent slippage between the timing belt 338 andthe print head and guide bushing assemblies, a toothed belt is providedand the clamping jaw 556 is provided with a surface corresponding to theconfiguration of the timing belt teeth, so that a positive lockingbetween the clamp and the timing belt is effected, thereby eliminatingall possibility of slippage during movement of the print head assembly.-

The print head may be manually retracted from its normal position withthe energizing pins in contact with the surface of the record paper forany purpose by means of a manually operated lever 560 secured to thecenter shaft 561 of the rotatable disc 501. As indicated previously, theguide shaft 336, upon which the print head assembly is mounted forsliding movement, is eccentrically secured to the rotatable discs 501and 502 such that rotation of the discs will effect a transversedisplacement of the guide shaft 336, and consequently also the printhead 334, in a direction substantially perpendicular to the surface ofthe platen 332. This action is seen most effectively in FIG. 13 whichhas been simplified for purposes of clarity. Clockwise rotation of thelever 560 (direction arrow c) from its vertical rest position willeffect a clockwise rotation of the guide shaft 336 about the center lineof the rotatable discs 501 and 502, thereby displacing the guide shaftand the print head assembly 534 in a direction away from the platen 332.Since the guide bearing assembly is freely rotatable upon the guide 8shaft 336, the print head 334 will not rotate with the lever 560 butwill be maintained in its normal upright position (phantom outline) bythe slide bar 550 riding in the slot 551.

In FIG. 10, it can be seen that the manual lever 560 is retained in itsrest position by an adjustable stop 562 and is biased into this restposition against the stop 562 by a spring 563 connected between a pin564 on the lever 560 and a pin 559 connected to the side support plate514. As will be indicated hereinafter in greater detail, it is necessarythat the print head be automatically retracted when it reaches the endof its scan so that the energizing pins on the print head are not incontact with the paper surface when the print head is reciprocated backto its starting position. This is accomplished automatically within themachine and thus the lever 560 is normally utilized only when theprinter is not in use.

For purposes of replacing the paper roll 538 and inserting the paperstrip beneath and around the platen 332 and between the print head andthe platen it is necessary not only to retract the pressure rollers butalso to simultaneously retract the print head assembly. For thispurpose, a pin 565 (FIGS. 6 and 14) is carried by the cam 535 and issecured to an operating lever 566 operatively connected to control lever567 by means of a pin 568 carried by the lever 566 riding in a slot 569in the control lever 567. The control lever 567 is also provided with anear 570 which contacts the stop 562 determining the rest or neutralposition of the control lever.

The control lever 567 is directly connected to the rotatable disc 501,as seen in FIG. 16, and is normally biased into its rest position Withthe car 570 against the stop 562 by the spring 563 (FIG. 10) connectedto the manual control lever 560. The control lever 560 being secured tothe center shaft 561 for the rotatable disc 501, the spring 563determines the neutral or rest position for the lever 560 and thecontrol lever 567, in turn properly positioning the print head withrespect to the platen 332.

When it is necessary to retract the pressure rollers on the platen 332in the print head assembly 334, such as when a new paper strip roll isto be inserted into the machine, rotation of the lever 530, as seen inFIG. 14, in a clockwise direction will effect a rotation of the cams 535and 536 thereby forcing the three sets of pressure rollers outwardlyaway from the platen 332 and will simultaneously actuate the lever 566by way of the pin 565 rotating the control lever 567 in a clockwisedirection against the normal bias of spring 563 and away from the stop562, thereby displacing the guide shaft 336 and the print head 334 in adirection away from the platen 332. When the lever 530 is rotated backto its initial position in the counter clockwise direction, the spring563 will effect a return of the guide shaft 336 through the disc 501,control lever 567, shaft 561 and manual lever 560.

The platen 332 is rotated during normal machine operation to effectadvance of the paper 330 automatically by means of a spring clutch 572located on the left side of the printer mechanism, as seen in FIGS. 68,which spring clutch 572 is actuated in the well-known manner by asuitable control linkage (FIG. 7). The automatic paper ad vancemechanism does not form a specific part of the instant invention and maybe provided in accordance With any conventional paper advance mechanismconstruction capable of effecting rotation of the platen 332 eitherautomatically or in response to control from the keyboard or othercontrol portion of the printer.

Single line paper advance may also be performed manually by rotation ofthe manual paper advance handle 26 located at the right side of theprinter, as seen in FIG. 8, which handle drives the platen via aunidirectional spring clutch. The operation of the lever 26 provides aforward advance of the paper equivalent to one printing line, and thespring clutch 574 slips when the lever is moved in a counter-clockwisedirection to the initial position in preparation for a forward advance.

The print head 334 is driven by means of the endless toothed belt 338looped around a driving pulley 580 and a driven pulley 581. As seen inFIG. 10, the pulley 581 is driven by means of a motor 582 mounted on theframe 500 of the printer. It should be noted that even though pulley 581is referred to as a driven pulley it functions as a driving pulley whenconsidering its relationship to belt 338. The driving function of pulley580 is discussed hereinbelow. Drive is obtained from the motor 582 viareduction gears 583 and 584 which effect rotation of drive shaft 585,supported by U-shaped support bracket 586' also mounted on the frame 500of the printer. The drive from shaft 585 is once again applied throughsuitable .reduction gears 587 and 588 to a drive shaft 589 which issupported, as seen in FIGS. 10 and 15, by a second U- shaped bracket 590mounted on the frame 500. The shaft 589 is supported on the frame 590 atthe forward end thereof adjacent the pulley 581 by a suitable bushing591 and at the rear portion of the mechanism by a sleeve 592 keyed tothe shaft 589 and supported within a guide bearing 593. The sleeve 592extends beyond the bearing 593 toward the pulley 581 and is providedwith a pair of collars 594 and 595 which serve to maintain the properposition of the sleeve 592 and the shaft 589, and prevent axial shiftingthereof.

The pulley 581 is mounted upon the drive shaft 589 on suitable bushings596 and 597 so that the pulley 581 may freely rotate regardless of thedrive provided by the shaft 589. An extension 598 on the pulley 581abuts with the sleeve 592 and has a diameter substantially identical tothis portion of the sleeve 592. A clutch spring 600 is positioned overboth the sleeve 592 and the extension 598 of the pulley 581 with one endof the spring secured at 599 to the sleeve 592. As a result of theclutch spring 600, drive from the drive shaft 589 may be applied to thepulley 581 through the sleeve 592 by actuating the clutch spring 600thereby effecting a connection between the sleeve 592 and the extension598 of the pulley 581.

The spring 600 is wound upon the sleeve 592 and the extension 598 ofpulley 581 such that normal rotation provided by the drive shaft 589will result in a tightening of the spring locking the sleeve 592 to thepulley 581 so long as some means is provided for holding the free end ofthe spring coil. It is therefore possible to activate and deactivate thespring clutch applying driving power and withdrawing driving power,respectively, from the pulley 581 by controlling the free end of theclutch spring 600.

The clutch interconnecting the drive shaft 589. and the pulley 581 isengaged by pressing a nylon shoe 601 (FIGS. and 16) against the outsidediameter of the free end of spring 600 thereby effectively holding orlocking the free end of the spring causing the spring to tighten up andlocking the sleeve 592 to the pulley 581. The nylon shoe 601 is mountedon the end of a spring loaded lever 602 pivoted at 603 to a frame member604 of the machine. The lever 602 is biased by spring 605 interconnectedbetween the levers 602 and a pin 606 mounted on the frame of themachine, so as to be biased in the direction of the spring 600. Alatching lever 607 is pivoted at 608 to the frame member 604 of themachine and is provided with a hook portion 609 which engages with alatch 610 on the lever 602, normally holding the lever 602 against thebias of spring 605 and preventing the shoe 601 from contacting theclutch spring 600.

The latching lever 607 is normally biased in the clockwise direction bya spring 611 interconnected between the lever 607 and a pivot pin 612fastened to the plate 604 of the machine. The end of the locking lever607 opposite the hook shaped end 609 communicates with an electromagnet615 which when energized, attracts the lever 607 causingcounter-clockwise rotation thereof against the bias of spring 611disengaging the hook shaped member 609 from the latch portion 610 on thelever 602.

The lever 602 is also provided with a cam follower 616 whichcommunicates with a cam portion 617 on a plate 10 618 secured to theinside surface of the pulley 581. Contact between the cam surface 617and the follower 616 effects a counter-clockwise rotation of the lever602 about the pivot shaft 603 against the bias of spring 605.

It can therefore be seen that the print operation is initiated byenergization of the electromagnet 615 which attracts the locking lever607 causing counter-clockwise rotation thereof against the bias ofspring 611. As a result of the counter-clockwise rotation of latchinglever 607, the hook-shaped end 609 disengages from the latching portion610 of the lever 602 and spring 605 will rotate the lever 602 in aclock-wise direction about the pivot shaft 603 urging the shoe 601 intocontact with the clutch spring 600. The constantly rotating shaft 589will then transfer its driving force through the sleeve 592 and thespring clutch 599 to the pulley 581 thereby driving the print head 334through the timing belt 338.

The print head begins its scan at the extreme left hand position of theguide shaft 336 and moves along the length of the guide shaft across thewidth of the paper 330. The driving pulley 581 is dimensioned so thatone complete revolution of the pulley will effect a reciprocation of theprint head 334 from its extreme left hand position to its extreme righthand position. By then positioning the cam surface 617 at a proper pointalong the circumference of the drive pulley 581, when the print head 334reaches its extreme right hand position, the cam surface 617 willcontact the follower 616 forcing the lever 602 to rotate in acounter-clockwise direction disengaging the shoe 601 from the spring600. The lever 602 is rotated at distance sufficient to re-engage thelatch portion 610 with the U-shaped portion 609 on the latching lever607 and since the electromagnet 615 is no longer activated, the shoe 601will be retained in this inactive position until the next print cycle isrequired.

As soon as the shoe 601 is disengaged from the clutch spring 600, thepulley 581 will be automatically disengaged from the drive shaft 589. Atthis point, a clock spring (not shown) within the driving pulley 580,which has been wound during the initial scan of the print head, willserve as a means for driving the pulley 580 and the pulley 581reciprocating the print head 334 back to its initial position.

The pulley 580 is also provided with a detent 619, seen in FIG. 6,within which a follower 620 carried by a lever 621 pivoted at 622 to themachine frame is biased so that the follower 620 is normally urged intothe detent 619 by a spring 623, interconnected between the lever 621 anda pin 624 on the machine frame. This combination serves to determine theinitial or start position of the print head more accurately since inreturning the print head to the start position, the pulley 580 willsubstantially completely lose the driving force from the spring thereinas the print head reaches the start position at the extreme left of theguide shaft 336, and at this time the follower 620 will drop into thedetent 619 holding the pulley 580 in this position. By this means, thestart position for the print head is accurately determined at all timesthereby insuring proper registration of the data that is printed sincethis registration is dependent upon the accurately time positioning ofthe print head after initiation of the print operation throughenergization of the electromagnet 615.

As seen in FIG. 8, a stop member 625 and spring 626 are positioned atthe extreme left end of the guide shaft 336 to help determine the startposition of the print head arrangement and cushion the arrival of theprint head at this position during the return excursion.

As indicated previously, it is necessary during return of the print headat the end of print scan to retract the print head so that theenergizing pins do not rest upon the record paper during return movementof the print head. The invention therefore provides a means forautomatically retracting the print head when it reaches the end of theprint scan and automatically returns the print head to the surface ofthe record paper as soon as the print head reaches the start position.

The print head retracting mechanism is illustrated in FIGS. 14-16. Alever 628 (also shown in FIG. 6) is loosely mounted at one end of pivotlever 629, which is rotatable about the pivot shaft 612 mounted on theframe 604 of the machine. The lever 628, as seen in FIGS. 15 and 16, isprovided with an ear 631 which limits clockwise rotation of the lever628 on the lever 629 and is connected via a spring 632 to a similar car633 on the lever 629. As a result of the bias provided by spring 632 thelever 628 is normally retained in a position with the car 631 in contactwith an edge of the lever 629.

A lever 635 is rigidly secured to the lever 629 between -the pivot shaft612 and the end carrying the lever 628 such that clockwise rotation ofthe lever 629 will result in a downward movement of the free end oflever 635 to which is connected an actuating lever 636 by suitablefastening means 637. The lever 636, as seen in FIG. 14, is connected tothe control lever 567 by means of a pin 638 riding in a slot 639.Downward movement (arrow d) of the lever 636 effects a clockwiserotation of the control lever 567 until the projection 640 on the lever567 overrides the lip 641 on a latching lever 642 thereby locking thecontrol lever 567 in the rotated position. As indicated above, clockwiserotation of the control lever 567 effects a clockwise rotation of therotatable disc 501 connected eccentrically to the guide shaft 336, whichin turn effects a retracting of the print head.

The above-described print head retract mechanism operates in thefollowing manner. As the print head reaches the extreme right-handposition of the print head scan, an extension 645 (FIG. 16) on the clampmember 556 on the print head guide assembly will strike the lever 628rotating the pivot lever 629 in a clockwise direction. It should benoted at this point that should the print head pass beyond the controllever 628 by any means, it can pass back over the control lever 628against the bias of spring 632 without effecting the position of lever629 during the return movement of the print head. -With the lever 629rotated in the clockwise direction, swinging the end of lever 635 in adownward direction, and actuating the control lever 636, the controllever 567 will be rotated in a clockwise direction and latched bylatching lever 642 holding the print head in the retracted positionduring the entire return excursion thereof. As the print head reachesthe start position during return movement thereof, a cam surface 650(FIG. 14) on the drive pulley 581 will contact the locking lever 642forcing it away from the control lever 567 until the projections andextensions 640 and 641 disengage permitting the spring 563 connected tothe manual control lever 560 to rotate the control lever 567 in thecounter-clockwise direction until the ear 570 contacts the stop 562,thereby repositioning the print head adjacent to the paper in the startposition.

Electrical energization of the print head is accomplished through theindividual cables 660 (FIG. 7) from the printer matrix, which cables 660are maintained in proper position during print head reciprocation by acable support and guide member 661 which is rotatably mounted to a framemember in the machine. The guided support member 661 serves as a meansfor maintaining the cables in alignment and providing sufiicient slackso as to prevent undue tension on the cables during reciprocation of theprint head.

Although a specific embodiment of the invention has been illustrated anddescribed in detail by way of example, it is to be understood that theinvention is not limited thereto. Various changes may be made in thedesign and arrangement of parts without departing from the spirit andscope of the invention as defined by the appended claims as will now beunderstood by those skilled in the art.

We claim:

1. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for reciprocal movement thereof across the width of saidmaterial,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate, motor meansfor energizing said driving means, clutch means and actuating meanstherefor for connecting said motor means to said driving means inresponse to a control signal, said clutch means comprising a shaftdriven by said motor means, a first hub afiixed to said shaft, a secondhub rotatably mounted on said shaft, and means responsive to saidactuating means for coupling said first and second hubs for conjointrotation about said shaft under conditions where said driving means isdriving said print head,

means for deactivating said clutch means automatically in response tosaid print head being moved to and occupying said other end of saidguide shaft means, said deactivating means operatively connected to saidresponsive means to decouple said hubs regardless of shaft rotation.

2. In a printer as set forth in claim 1 wherein said guide shaft meansis mounted eccentrically for movement with respect to said recordmaterial in response to rotation thereof, and including control meansfor automatically moving said guide shaft means away from said recordmaterial in response to said print head being moved to and occupyingsaid other end of said guide shaft means.

3. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for movement thereof across the width of said material,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate,

motor means for energizing said driving means, and

a spring clutch and actuating means therefor for connecting said motormeans to said driving means in response to a control signal,

said driving means including guide belt means secured to said print headand pulley means operatively supporting said guide belt means forrotation, said driving means further including means for biasing saidpulley means and said print head into a neutral position underconditions where said driving means is not driving said print head, saidprint head being disposed at said one end of said guide shaft means whensaid neutral position is effected.

4. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for movement thereof across the width of said material,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate,

motor means for energizing said driving means,

clutch means and actuating means therefor for connecting said motormeans to said driving means in response to a control signal,

said clutch means including a driven element, a driving element coupledto said driving means and concentric with said driven element, a springelement secured to said driven element and encompassing a portion ofsaid driving element, and means for selectively fixing said springelement with respect to said driving element in response to saidactuating means. 5. In a printer as set forth in claim 4 wherein saidactuating means includes electromagnet means for actuating said meansfor selectively fixing said spring element.

6. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprcating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for movement thereof across the Width of said material,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate,

motor means for energizing said driving means,

clutch means and actuating means therefor for connecting said motormeans to said driving means in response to a control signal, means fordeactivating said clutch means automatically in response to said printhead being moved to and occupying said other end of said guide shaftmeans,

said clutch means including a driven element, a driving element coupledto said driving means and concentric with said driven element, a springelement secured to said driven element and encompassing a portion ofsaid driving element, and means for selectively fixing said springelement with respect to said driving element in response to saidactuating means,

said actuating means including electromagnet means for actuating saidmeans for selectively fixing said spring element,

said means for deactivating said clutch means including cam meanssecured to said driving element for deactivating said means forselectively fixing said spring element.

7. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for movement thereof across the Width of said material,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate,

motor means for energizing said driving means,

clutch means and actuating means therefor for connecting said motormeans to said driving means in response to a control signal,

said guide shaft means being mounted eccentrically for movement withrespect to said record material in response to rotation thereof,

control means for automatically moving said guide shaft means away fromsaid record material in response to said print head being moved to andoccupying said other end of said guide shaft means,

said control means including a control lever, a latching lever forlocking said control lever in the rotated position and cam means on saiddriving means for deactivating said latching lever in response to saidprint head being moved to and occupying said one end of said guide shaftmeans.

8. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head travers ing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for movement thereof across the width of said material,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate,

motor means for energizing said driving means,

clutch means and actuating means therefor for connecting said motormeans to said driving means in response to a control signal,

said guide shaft means being mounted eccentrically for movement withrespect to said record material in response to rotation thereof,

control means for automatically moving said guide shaft means away fromsaid record material in response to said print head being moved to andoccupying said other end of said guide shaft means,

said print head being freely rotatably mounted on said guide shaftmeans, and guide means secured to said print head for retaining saidprint head in a given disposition with respect to said record material,

said guide means including a guide member having a slot in spacedparallel relationship with said guide shaft means and a guide bar havingone end thereof secured to said print head and the other end thereofriding in said slot.

9. In a printer for printing electrically on electro-sensitive recordmaterial by means of a print head'tranversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for supporting said print head adjacent said recordmaterial for movement thereof across the width of said material,

driving means for driving said print head from one end of said guideshaft means to the other at an essentially constant rate,

motor means for energizing said driving means,

clutch means and actuating means therefor for connecting said motormeans to said driving means in response to a control signal,

said driving means including a guide belt means secured to said printhead and pulley means supporting said guide belt means for rotation,said driving means further including means for biasing said pulley meansand said print head into a neutral position under conditions where saiddriving means is not driving said print head, said print head beingdisposed at said one end of said guide shaft When said neutral positionis effected, and

detent means for positively determining said neutral position of saidpulley means.

10. In a printer as set forth in claim 9 wherein said guide shaft meansis mounted eccentrically for movement with respect to said recordmaterial in response to rotation thereof, and including control meansfor automatically moving said guide shaft means away from said recordmaterial in response to said print head being moved to and occupyingsaid other end of said guide shaft means, 1 means for deactivating saidclutch means automatically in response to said print head being moved toand occupying said other end of said guide shaft means,

said clutch means including a driven element, a driving element securedto said pulley means concentric with said driven element, a springelement secured to said driven element and encompassing a portion ofsaid driving element, and means for selectively fixing said springelement with respect to said driven element in response to saidactuating means,

said actuating means includingelectromagnet means for actuating saidmeans for selectively fixing said spring element,

said means for deactivating said clutch means including cam meanssecured to said pulley means for deactivating said means for selectivelyfixing said spring element,

said control means including a control lever, a latching lever forlocking said control lever in the rotated position and cam means on saidpulley means for deactivating said latching lever in response to saidprint head being moved to and occupying said one end of said guide shaftmeans,

said print head being freely rotatably mounted on said guide shaftmeans, and guide means secured to said print head for retaining saidprint head in a given disposition with respect to said record material,

said guide means including a guide member having a slot in spacedparallel relationship with said guide shaft means and a guide bar havingone end thereof secured to said print head and the other end thereofriding in said slot.

11. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head, a cylindrical platen foraccommodating the record material, a guide shaft for slidably supportingsaid print head, means for mounting said guide shaft parallel to saidplaten and adapted to permit engagement between said print head and therecord material during an excursion across the width of said material,

timing belt means secured to said print head for driving said print headand including a driving pulley and a driven pulley and an endless beltsupported by said pulleys in parallel relationship with said shaft,

motor drive means for driving said driving pulley at an essentiallyconstant rate, said driving pulley being normally disconnectedtherefrom,

clutch control means for selectively connecting said motor drive meansto said driving pulley in response to a control signal,

said clutch control means including spring clutch means for connectingsaid motor drive means to said driving pulley when actuated, andactuating means for actuating said spring clutch means in response tosaid control signal, and means for driving said print head in a returnexcursion along said shaft when said driving pulley is disconnected fromsaid motor drive means.

12. In a printer as set forth in claim 11 wherein said mounting meansincludes eccentrical support means for said shaft adapted for rotationto move said shaft and print head about an axis parallel to the recordmaterial, and

said print head is freely rotatably mounted on said guide shaft, andincluding guide means secured to said head for maintaining said printhead in a given disposition with respect to said record material.

13. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for guiding said print head adjacent said recordmaterial, during movement thereof across the width of said material,

' timing belt means secured to said print head for driving means and aguide shaft supported by said eccentric support means for conjointmovement of said shaft and print head with respect to the recordmaterial,

said print head being freely rotatably mounted on said guide shaft, andguide means secured to said print head for maintaining said print headin a given disposition with respect to said record material,

said guide means including a guide member having a slot in spacedparallel relationship with said guide shaft means and a guide bar havingone end thereof secured to said print head and the other end thereofriding in said slot.

14. In a printer as set forth in claim 13 and including control linkagemeans for actuating said eccentric support means to retract said printhead automatically in response to said print head reaching apredetermined position along said guide shaft.

15. In a printer for printing electrically on electrosensitive recordmaterial by means of a print head traversing said record material in acontinuous movement in a reciprocating manner,

print head means including a print head,

guide shaft means for guiding said print head adjacent said recordmaterial during movement thereof across the width of said material,

timing belt means secured to said print head for driving said print headat an essentially constant rate including a driving pulley and a drivenpulley and an endless beltsupported by said pulleys,

motor drive means for driving said driving pulley being normallydisconnected therefrom,

clutch control means for selectively connecting said motor drive meansto said driving pulley in response to a control signal,

said clutch control means including spring clutch means for connectingsaid motor drive means to said driving pulley when actuated, andactuating means for actuating said spring clutch means in response tosaid control signal,

said actuating means including a spring actuating member normallylatched in an inoperative position and control means for selectivelyreleasing said spring actuating member in response to said controlsignal,

said timing belt means including means for latching said springactuating member in said inoperative position after one completerotation of said driving pulley,

the circumference of said driving pulley being equal to the length ofthe path of movement of said print head such that one complete rotationof said pulley produces one complete scan of said print head.

16. In a printer as set forth in claim 15 and including bias meansassociated with said driven pulley for biasing said pulley in a givenposition wherein said print head is in its start position such thatrotation of said driven pulley must be effected against the bias of saidspring means,

said guide shaft means including eccentric support means and a guideshaft supported by said eccentric support means for conjoint movement ofsaid shaft and print head with respect to the record material,

said print head being freely rotatably mounted on said guide shaft, andguide means secured to said print head for maintaining said print headin a given disposition With respect to said record material,

said guide means including a guide member having a slot in spacedparallel relationship with said guide shaft means, and a guide barhaving one end thereof secured to said print head and the other endthereof riding in said slot,

detent means for positively determining the position of said drivenpulley corresponding to the start position of said print head,

, control linkage means for actuating said eccentric supresponse to saidprint head reaching a predetermined position along said guide shaft.

References Cited by the Examiner UNITED STATES PATENTS Soblik 19755Fanshow 1976.4 Garbell 197138 Bower 197138 Zabriskie 34674 X 10Zabriskie 346-74 Alden 346139 Palmer et al 19716 Palmer 197-16 Richter346-74 Dirks 147-1 Epstein et al 17830 X Palmer 19716 Wales 1971Schiefeler 197-1 Ayres 197-11 ROBERT E. PULFREY, Primary Examiner. DAVIDKLEIN, Examiner.

E. S. BURR, Assistant Examiner.

1. IN A PRINTER FOR PRINTING ELECTRICALLY ON ELECTROSENSITIVE RECORDMATERIAL BY MEANS OF A PRINT HEAD TRAVERSING SAID RECORD MATERIAL IN ACONTINUOUS MOVEMENT IN A RECIPROCATING MANNER, PRINT HEAD MEANSINCLUDING A PRINT HEAD, GUIDE SHAFT MEANS FOR SUPPORTING SAID PRINT HEADAD JACENT SAID RECORD MATERIAL FOR RECIPROCAL MOVEMENT THEREOF ACROSSTHE WIDTH OF SAID MATERIAL, DRIVING MEANS FOR DRIVING SAID PRINT HEADFROM ONE END OF SAID GUIDE SHAFT MEANS TO THE OTHER AT AN ESSENTIALLYCONSTANT RATE, MOTOR MEANS FOR ENERGIZING SAID DRIVING MEANS, CLUTCHMEANS AND ACTUATING MEANS THEREFOR FOR CONNECTING SAID MOTOR MEANS TOSAID DRIVING MEANS IN RESPONSE TO A CONTROL SIGNAL, SAID CLUTCH MEANSCOMPRISING A SHAFT DRIVEN BY SAID MOTOR MEANS, A FIRST HUB AFFIXED TOSAID SHAFT, A SECOND HUB ROTATABLY MOUNTED ON SAID SHAFT, AND MEANSRESPONSIVE TO SAID ACTUATING MEANS FOR COUPLING SAID FIRST AND SECONDHUBS FOR CONJOINT ROTATION ABOUT SAID SHAFT UNDER CONDITIONS WHERE SAIDDRIVING MEANS IS DRIVING SAID PRINT HEAD, MEANS FOR DEACTIVATING SAIDCLUTCH MEANS AUTOMATICALLY IN RESPONSE TO SAID PRINT HEAD BEING MOVED TOAND OCCUPYING SAID OTHER END OF SAID GUIDE SHAFT MEANS, SAIDDEACTIVATING MEANS OPERATIVELY CONNECTED TO SAID RESPONSIVE MEANS TODECOUPLE SAID HUBS REGARDLESS OF SHAFT ROTATION.